Debates are discussions not speeches. They are supposed to be a test of the candidates' ability to reason out an argument "on his feet." They are not supposed to be little "canned speeches" but a process of argumentation and back and forth discussion that demonstrates the candidate's depth of understanding and his ability to present his arguments in a convincing manner. Using a teleprompter shows weakness and defeats the purpose of a debate. Each candidate should know their own positions well enough to argue them unaided.